14:2 SPECIAL SENSES. 



ocular portion, furrowed, and presents small, isolated papillae 

 near the borders of the lids, which increase in number and 

 size toward the folds. This portion of the membrane pre- 

 sents large capillary blood-vessels and lymphatics, and is cov- 

 ered with a layer of cells of flattened epithelium. The scle- 

 rotic portion is thinner, less vascular, and has no papillae. It 

 is covered by conical and rounded epithelial cells, which pre- 

 sent from two to four layers. Over the cornea, the epithe- 

 lium of the sclerotic portion is continued in delicate, trans- 

 parent layers, without a distinct basement membrane. 



The nerves of the ocular portion of the conjunctiva and 

 the folds have a peculiar termination in simple bulbs, ob- 

 served by Krause, which have already been described. 1 This 



t/ t/ 



appearance of bulbs is thought by some to be artificial and 

 due to extravasation of myeline in making the prepara- 

 tions; but they are regarded as true bulbs by many high 

 authorities. 3 



The Lachrymal Apparatus. The eyeball is constantly 

 bathed in a thin, watery fluid which is secreted by the lach- 

 rymal gland, is spread over the globe by the movements of 

 the lids and of the eyeball, and is prevented, under ordinary 

 conditions, from overflowing upon the cheek, by the Mei- 

 bomian secretion. The excess of this fluid is collected into 

 the lachrymal sac and is carried into the nose by the na- 

 sal duct. The lachrymal gland, the lachrymal canals, duct, 

 and sac, and the nasal duct, constitute the lachrymal appa- 

 ratus. 



The lachrymal gland is an ovoid, flattened gland of the 

 racemose variety, resembling the salivary glands in its gen- 

 eral structure. It is about the size of a small almond, and is 

 lodged in a shallow depression in the bones of the orbit at its 

 upper and outer portion. It is closely attached to the perios- 



1 See vol. iv., Nervous System, p. 42. 



2 STRICKER, Manual of Human and Comparative Histology, The New Syden- 

 ham Society, London, 1873, vol. iii., p. 453, et seq. 



